In recent years there has been considerable interest in intravenous delivery pumps for the feeding of saline solutions, and the like, or blood, to a patient. For many years such materials were fed to a patient only by the force of gravity which necessitated placing the container containing the liquid for delivery to the patient at a considerable elevation above the patient. These devices were not entirely satisfactory in view of the height requirement and the difficulty in accurately regulating their flow. Regulation could only be secured by a hand-set tube clasp, and control was secured by counting the drops of fluid in a predetermined time -- and then periodically checking by a nurse to determine that the desired rate of delivery was being maintained. Gravity flow made it very difficult to maintain a regulated flow over a prolonged period of time. Therefore, in recent years there has been a trend toward developing a positive acting pump which could be accurate in its delivery of intravenous feeding material to the patient, could be readily adjusted and would be positive in its operation without requiring the placing of the bottle at some distance above the patient. The pump also should be free from a rubbing contact between parts, as that would be destructive to the pumping of blood. Most pumps heretofore suggested have been rather expensive and hence could not be used once and then thrown away. Such pumps were difficult to disassemble, sterilize and re-assemble so that sterilization and maintenance of sterile conditions are difficult.
In the present invention, the beneficial results are secured by a positive displacement plunger operating in a chamber only slightly larger than the plunger; providing the plunger, which extends through a wall of the chamber, with a resilient sheath sealed to the wall of the chamber so that there could be no contamination from the outside of the material being pumped and there would be no rubbing contact between any member with another where either was in contact with fluid being pumped. The pump is quite small, being approximately only 2 inches in height when viewed from the side, as shown in FIGS. 1 and 2. the pump of the present invention can readily be made of light plastic material, contains few parts, is constructed of material which is relatively inexpensive, so that the pump can be sold cheaply enough to be thrown away with each use.